4d-6d finish nails will work for this shoe molding. Predrill because of hardness of Brazilian Walnut. Flooring; Brazilian Walnut is 182% harder than red oak. Cleat nailers rather than staples have a better chance of penetrating the harder exotics. Better chance for 5/16", 3/8", and 1/2" is a 18 and 20 gage nail with a 50P or 200 POWERNAIL nailer. 18 gage with a 50P and a 3/4" adapter plate can work best on very hard 3/4"exotics. Or equivalent nailer.

If Hand Nailing is Necessary-One person can pre-drill the nail holes with a 3/32" (2mm) bit, the next can complete the nailing. For boards 2 1/4"-3 1/2" wide place a 2" nail, every 8”-10” inches along the side tongue edge and 2"-3" from the board ends. The wider the board the closer the nail spacing.Use- galvanized or regular finishing nails 6d-7d.